I've never owned a hippo, but I have gotten rid of ich a couple times with a diatom filter. (not repeat infestations, but newly acquired fish in QT)
Basically I just freshwater dipped and let the diatom filter run for a few weeks on the QT. It claims to filter out anything larger than 1 micron, which includes the swimming stages of ich.
I was skeptical, but it has worked a couple times. I guess the idea is that your fish fights off the ones already on it, and the filter removes the swimming ones from the tank.
I ran normal salinity and no meds of any kind, just used the filter constantly for a few straight weeks. It seemed to work completely, and had no kind of adverse effects at all. I think it was about $100 from a LFS, and has eliminated ich from QT a few times now (as opposed to the cost of copper, test kits, fish dying from copper exposure, etc).
I've also used it in my QT a few times just to clean up the tank some (using a turkey baster to stir up the junk & let it filter it out).